For a week now, my coworker and I have been troubleshooting a machine which has been displaying some crazy behavior. HMI values were changing on their own. Some of the stations disabled themselves. Never seen anything like this. The first thing we started with was the processor (SLC 5/04), then the PLC power supply, the HMI and all associated wiring back to the PLC has been changed. We then put in a known good appliance 24VDC power supply that powers the rest of the machine with 24VDC. After these things were changed out, some things that were affected before are not displaying the same behavior (counts, stations disabling themselves), but the one thing that is still happening is that some CTU presets are changing on their own. The pass part & total part count was always set to some number that was unreachable in a weeks production much less in a day. It was set at zero for both of these totals. Also, in one of the assembly stations, there is a counter to see 'x' bad parts in a row and throw a fault. Normally these are set at 3 and yesterday I found it at 46.
I'm unsure where to look next. Thinking about changing the chassis/rack.
General Background: The machine has a DC motor to rotate a dial for station indexing. Nests move around 12 stations. There are pneumatic presses and servos on the machine. The machine also has a sibling machine that is working fine built to the same specs so I have something to compare things with.
Looking for any suggestions. Thanks in advance!!!
I'm unsure where to look next. Thinking about changing the chassis/rack.
General Background: The machine has a DC motor to rotate a dial for station indexing. Nests move around 12 stations. There are pneumatic presses and servos on the machine. The machine also has a sibling machine that is working fine built to the same specs so I have something to compare things with.
Looking for any suggestions. Thanks in advance!!!